Bacterial leaf spot is caused by the bacterium Xanthomonas campestris pv. vesicatoria. This disease starts out rather nonchalantly with small yellowish green spots on the plants surrounded by a yellowish halo. The yellow extends on the leaves and the spots turn to brown then black and may look sunken. The tissue in the center may dry out and break away. If it is wet outside the spots may become water soaked. Some leaves may continue to yellow and drop off, this will lead to fruit developing sun scald. The fruit may also develop scab like spots. This is a very serious disease in pepper and is of particular concern in warm moist conditions. Well, humidity and heat are the name of our game in Central Texas in the summer! This same disease effects tomatoes.
First Line of Defense Healthy plants are the first line of defense. Make sure to buy transplants from a certified grower. Look to make sure the transplants are disease free.
Make sure your seed companies are certified. Rotate your pepper crops each year so that you so not spread the disease.
Do not work with wet plants as this spreads the disease.
Compost is a good way to arrest the pathogen.
Mulching around your pepper plants keeps water from splashing on them and that keeps the pathogen from spreading.
When buying seeds make sure that they have been heat treated or heat treat them yourself this is the only way to make sure that you will not spread the disease.
Treat Seeds Your best line of defense is to heat treat your seeds start by using a good dairy or laboratory thermometer. Put a metal washer in the bottom of a cheesecloth so it will sink. Fill the cheesecloth half full of seeds. Fill a pan with water and heat to 125° F (51 ° C). Soak seeds at 125 ° F for 30 minutes while agitating the cheesecloth with seeds the entire time. It is important to keep the temperature constant and keep the water bath agitated. After 30 minutes, dip the bag in cold water to stop the heat treatment. Spread the seeds out to dry and apply a protective seed-treatment fungicide. Freshly harvested seed withstand the heat treatment better than do 1- or 2-year old seed.
Copper Oxide Make sure that there is plenty of room for your plants to get proper air circulation. It helps when you have an infestation on your cole crops to pick off the old leaves on the kale and collards and compost them. The leaves will grow back.
Bacillus subtilis QST 713 is a common bacterium found in soil water and air. It is effective by competing for resources and by colonizing and attaching itself to fungal pathogens that you are trying to get rid of.